Traveling sprinklers that are adapted to follow an above-ground water supply pipe, and to engage in succession a number of water supply valves located along the pipe, are described in various prior patents, among them U.S. Pat. Nos. 3,575,200; 3,970,102; 3,984,052; and 4,240,461. There are other traveling irrigation machines known as “linear move” or “lateral move” machines that include large wheel-supported booms fitted with multiple sprinkler devices, where the drive tower is adapted to engage and actuate a forward supply valve before a trailing valve is disengaged so as to ensure continuous flow to the sprinklers supported on the machine. Representative examples are described in U.S. Pat. Nos. 4,442,976; 4,182,493 and 3,608,825.
The various machines described in the above patents have significant drawbacks and disadvantages, to the extent that there are few if any successful machines of this type on the market today. In fact, the most successful of the “linear move” machines are designed to draw water from a canal running alongside the field (see, for example, U.S. Pat. No. 5,080,290), or to utilize “drag hoses” that enable the machine to move from one end of the field to the other so as to eliminate the need for intermittent coupling to supply valves (see, for example, U.S. Pat. No. 4,350,295). The latter machines, however, also have drawbacks. For example, canal water is often dirty and can foul and clog the valves, sprinklers and other components. Drag hoses require constant attention and have to be relocated each time the machine reaches the end of a field.
In still other cases, complex mechanisms have been proposed for automatic docking with hydrants spaced along the length of a water supply pipe. One of the problems with these arrangements is that the hydrant risers must be held firmly in concrete, or welded onto steel pipe. In addition, alignment or docking mechanisms have been complex and costly to maintain. As a result, reliable docking under various conditions has proven to be an elusive goal. There remains, therefor, a need for a traveling sprinkler or irrigation device that moves into engagement, or docks with, and actuates, successive water supply valves located along a water supply pipe in a simple, cost-effective and reliable manner.